Revert "Detect High DPI on Linux Desktop"

[akshayaurora]

Reverts #8147

Previous way of using size difference between Window.size and Windows.get_DrwableSize is the correct way as outlined by SDL2 Documentation too.

The reason on why currently on Wayland window reports both to be the same cause apparently we are not properly using Wayland window provider.

[misl6]

LGTM!

[jotoft]

@akshayaurora can you explain in more detail what the issue with the original pull request was? The window size vs drawable area size is still the primary way of detecting the DPI in this PR.

The display DPI was just a secondary way of getting the DPI in case the primary way fails.

Without this PR there is no support at all for detecting DPI so the scaling does not work at all on Linux.

[akshayaurora]

The problem with that pr is that it tries to work around on get_gl_size not working.

get_gl_size is supposed to give a dpi adjusted size. It only supposed to work on Linux when using wayland(SDL2 Window provider with the video driver set to wayland).

Your solution worked around the issue trying to detect display dpi directly. Which is not supposed to be accurate even according to the documentation on SDL2 itself.

Correct solution here is to figure out why the get_gl_size is reporting same as Window.size/system_size instead of dpi adjusted size.(Probably need to properly enable wayland video driver but needs a bit more investigation)

1)Figure out why get_gl_size is not working/reporting correct size. i.e If we are not accurately setting the video driver or not compiling the required wayland support then that needs to be fixed.(This would fix things for the binary wheel installations on linux).

2. We probably need to detect env i.e Wayland/X11/FBO and then adjust scaling appropriately.

Your pr was a step in right direction just needs a bit adjustment to account for the above.

[FilipeMarch]

The dpi calculation is clearly wrong on my laptop

from kivy.app import runTouchApp
from kivy.uix.label import Label

runTouchApp(Label(text="hello world"))

This is how Hello World app should look like

This is how it looks like on my laptop (Arch Linux, kivy==master)

All my apps are completely distorted on my laptop screen 😫

This is my laptop screen config (not sure if this matters)

This is how kivy==master vs kivy==2.1.0 looks like on my laptop

Printing the DPI in kivy==master

>>> dpi: 189.02325439453125

Printing the DPI in kivy==2.1.0

>>> dpi: 96.0

Temporary workaround for me is adding this line on the end of _update_density_and_dpi method on kivy.core.window.window_sdl2.WindowSDL class on kivy==master

self.dpi = 96.0